Delay to therapy following controlled atrial shock therapy request

ABSTRACT

An implantable cardiac device detects a patient therapy request originating from external to the implantable device. A shock therapy delay period is timed in response to the detection of the patient therapy request. Atrial shock therapy is provided to the patient after expiration of the shock therapy delay period (if the presence of an ongoing atrial arrhythmia is detected). The patient therapy request may be provided by a patient activator including a magnet for operating a reed switch in the implanted device to provide the request. A patient activator including an input and receiver/transmitter circuitry may be employed to request the immediate providing of atrial shock therapy, and/or to set the duration the shock therapy delay period. By allowing specific delays to therapy after a therapy request, a patient can prepare for the requested therapy and thereby mitigate therapy discomfort.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. patent Ser. No. 10/643,513,filed on Aug. 19, 2003, now issued as U.S. Pat. No. 7,024,240, which isa continuation of U.S. patent Ser. No. 09/839,123, filed on Apr. 20,2001, now issued as U.S. Pat. No. 6,618,617, the specifications of whichare incorporated herein by reference.

FIELD OF THE INVENTION

The present invention pertains generally to medical devices and moreparticularly to implantable medical devices such as devices formonitoring activity of the heart and providing electrical shock therapythereto including automatic implantable cardioverter defibrillatordevices for treating atrial arrhythmias and external patient operabledevices for controlling the operation of such implantable medicaldevices.

BACKGROUND OF THE INVENTION

Various types of medical devices are employed to monitor electrical orother activity of the heart and to provide therapy to the heart inresponse to the detection of irregular cardiac rhythms. Such devices maybe implantable beneath the skin of a patient, i.e., in the patient'schest. Such implantable devices include a hermetically sealed canistercontaining electronic circuitry for implementing the functions of thedevice, one or more electrodes implanted in one or more of the chambersof the heart, or in close proximity thereto, and leads for connectingthe electrodes to the circuitry within the device canister. The devicecircuitry includes circuitry for detecting electrical signals producedby the heart, which signals are picked up at the electrodes, along withcircuitry, typically implemented in a microprocessor, for analyzing thethus-detected cardiac signals. The device may also include circuitry forproviding therapy in the form of electric shock signals applied to theheart. Such signals are provided to the heart, via the leads andelectrodes mounted in the heart, in response to the detection of anirregular cardiac rhythm by the analysis circuitry based on the detectedcardiac activity signals. The implantable device may also include atransmitter/receiver, for transmitting cardiac activity and otherinformation to an external device for, e.g., storage and/or furtheranalysis, and for receiving information, such as programminginstructions, from the external device via, for example, an RF link.

An example of such an implantable cardiac device is an automaticimplantable cardioverter defibrillator (AICD) for treating atrialarrhythmias, e.g., atrial tachycardia, fibrillation, flutter, etc. (Thefunctionality of an atrial AICD may be combined with those of abradycardia pacemaker, ventricular defibrillator, etc., in a singleimplantable device.) Atrial arrhythmias are probably the most commoncardiac arrhythmia. Although atrial arrhythmias are not usuallylife-threatening, patients with atrial arrhythmias generally experiencepalpitations of the heart, and may experience dizziness or even loss ofconsciousness. Atrial arrhythmias, such as atrial fibrillation, alsohave been associated with strokes and other conditions. Atrialarrhythmias can occur suddenly. Implantable atrial cardioverterdefibrillators are programmed to detect the onset of atrial arrhythmiasand to provide an appropriate electrical shock therapy to the atria toterminate the atrial arrhythmia. The atrial shock therapy to be providedmay depend upon the type of atrial arrhythmia detected, e.g., atrialtachycardia versus atrial fibrillation. Shock therapy provided by animplantable atrial cardioverter defibrillator may include a relativelyhigh voltage level atrial defibrillation or cardioversion pulse, whichis typically delivered to the atria in synchronism with a detected orpaced ventricular activation, to terminate atrial fibrillation orflutter. Atrial antitachycardia pacing may be applied by the implantabledevice to terminate atrial tachycardia. Atrial antitachycardia pacingtypically involves a train of pacing pulses applied to the atria at arate slightly higher than the rate of the tachycardia.

Various systems and methods have been developed to allow patients havingimplanted atrial cardioverter defibrillators to monitor and control, toat least some degree, operation of the implanted device. For example,U.S. Pat. No. 5,490,862 describes an implantable atrial defibrillatorwhich may be programmed to operate in a patient activated mode ofoperation. In the patient activated mode, an atrial fibrillationintervention sequence is performed by the implanted device in responseto the receipt of a sequence command generated from external to thepatient. The sequence command may be generated, for example, by anexternal magnet applied by the patient to near the implantation site, toclose and then open a reed switch mounted in the implanted device andcoupled to the device microprocessor. The intervention sequence thusinitiated by the patient, when he believes he is experiencing an atrialarrhythmia, includes atrial fibrillation detection by the implanteddevice and, if atrial fibrillation is confirmed, the application ofcardioverting electrical energy to the atria.

U.S. Pat. No. 5,674,249 describes the use of a portable communicationdevice which allows a patient to monitor and control the operation of animplanted atrial defibrillator. The portable communication device, whichmay be dimensioned to be hand held by a patient, includes atransmitter/receiver for communicating with the implanted device via atelemetry (e.g., RF) link. In this system, an atrial fibrillationintervention sequence may be initiated in an implanted device inresponse to a sequence command generated from the portable communicationdevice. The patient may also use the portable communication device toprogram the implanted device into an automatic mode, wherein theintervention sequence is initiated automatically at predetermined times.The handheld portable communication device receives an acknowledgmentsignal from the implanted device when a command signal sent from thecommunication device is received by the implanted device. The receipt ofthe acknowledgment signal by the portable handheld communication deviceis displayed to the patient on the device. The display includes adescription of the task being performed by the implanted device inresponse to the command signal sent by the patient. Thus, a patient isable both to monitor and control operation of an implanted cardiacdevice to some degree.

U.S. Pat. No. 5,999,851 describes an implantable atrial defibrillatorwhich includes an atrial fibrillation detection only mode of operation.In this mode, atrial fibrillation detection is initiated in theimplanted device by a command signal sent from an external patientoperated communication device, which is in communication with theimplanted defibrillator via a telemetry (e.g., RF) link. If atrialfibrillation is detected by the implanted atrial defibrillator, anappropriate signal is communicated to the patient operated communicationdevice, and a visual and/or audible message is provided by thecommunication device to the patient to indicate whether or not atrialfibrillation is detected. In this detection only mode, a further signalmust be provided from the communication device to the implanted deviceto initiate cardioversion therapy, preferably after continued atrialfibrillation is confirmed by the implanted device.

In each of the systems described above, atrial fibrillation detection,or atrial fibrillation detection followed by atrial shock therapy, ifrequired, may be initiated by a patient using an external communicationdevice. In each case, where atrial shock therapy is requested by thepatient, shock therapy is delivered by the implanted device immediatelyafter it is requested by the patient (perhaps after a slight delay toconfirm the presence of an atrial arrhythmia and to synchronize theatrial shock therapy delivery to a ventricular activation). The deliveryof shock therapy to a patient's heart can cause great discomfort to thepatient. If shock therapy is delivered essentially immediately followinga patient's request, the patient's ability to prepare for the therapy orto mitigate the discomfort of the therapy before therapy delivery isseverely limited. For example, a patient may wish to take analgesics ora sedative, lie down, or take other measures, such as begin exercises(calisthenics), or go to sleep, to mitigate shock perception beforeatrial shock therapy is provided by an implanted device. Currentsystems, in which patient requested atrial shock therapy is providedessentially immediately following a therapy request, do not allowpatients to make many of these preparations. It would be difficult for apatient to simultaneously exercise and request atrial shock therapyusing a conventional system for patient requested shock therapy, if thepatient wished to reduce shock perception using exercise. Similarly, itwould be impossible for a patient to go to sleep and then initiate anatrial shock therapy request using a conventional system.

What is desired, therefore, is a system which allows a patient tocontrol the providing of atrial shock therapy by an implanted device andin which the providing of therapy is delayed by a specific delay periodafter shock therapy is requested. The therapy delay period is preferablylong enough for the patient to prepare for the application of shocktherapy (e.g., by exercise, sleep, etc.) after a shock therapy requestis made. Preferably, a patient is also able to adjust the therapy delayperiod and select whether shock therapy will be provided immediatelyupon request or after expiration of the delay period.

SUMMARY OF THE INVENTION

The present invention provides a system and method which allows apatient with an implanted automatic implantable cardioverterdefibrillator to delay the providing of shock therapy to the atria bythe implanted device in response to a patient request for shock therapy.In accordance with the present invention, a patient employs an externalactivator communication device to request therapy from an implanteddevice. A shock therapy delay period is timed by the implanted device inresponse to the patient therapy request. An appropriate atrial shocktherapy is provided by the implanted device after expiration of theshock therapy delay period (preferably after confirmation of an ongoingatrial arrhythmia). The patient may be allowed to select the therapydelay period, and/or to select whether patient requested atrial shocktherapy is provided by the implanted device immediately following atherapy request or after expiration of the shock therapy delay period.

The present invention may be implemented in an implantable cardiacdevice, such as an automatic implantable cardioverter defibrillator,which provides atrial arrhythmia detection and electrical shock therapyto the atria to terminate such atrial arrhythmias. (The implantabledevice may also provide ventricular arrhythmia monitoring andventricular shock therapy functionality and/or ventricular pacingfunctionality, as well as atrial pacing capability.) The implantablecardiac device includes signal detection circuitry, connected via leadsto electrodes positioned in the atria and, preferably, the ventricles ofthe heart, to detect electrical heart activity signals. An implanteddevice system processor monitors the output provided by the signaldetection circuitry to detect the occurrence of an atrial arrhythmia,e.g., atrial tachycardia, fibrillation, and/or flutter, using knownatrial arrhythmia detection algorithms. The implantable device includescardioverter/defibrillator circuitry, controlled by the deviceprocessor, for providing defibrillation shock therapy, and/orantitachycardia pacing, depending upon the type of atrial arrhythmiaidentified, to the atria via the leads and electrodes implanted in theheart. The implantable device is preferably also provided with atelemetry receiver/transmitter, coupled to the device processor, toallow the processor to transmit cardiac activity and other data to anexternal programmer device for storage and/or further analysis, and toreceive data, such as programming instructions, from the externalprogrammer device. (The external programmer device is a relativelycomplicated device used by a physician to program the implanted deviceand query cardiac activity data therefrom.)

In accordance with the present invention, a patient, having an implantedcardiac device in accordance with the present invention, is able tocontrol the providing of atrial shock therapy by the implanted deviceusing a patient activator communication device. The patient activator ispreferably a relatively small, handheld device, which allows the patientto send a patient therapy request to the implanted device to control theproviding of shock therapy to the atria by the implanted device toterminate an atrial arrhythmia event. The patient activator preferablyemploys a relatively simple mechanism for providing a patient therapyrequest. For example, the patient activator may include a magnet which,when placed near the implantation site of the implanted device, operatesa reed switch in the implanted device, which is coupled to the implanteddevice processor, thereby to provide a patient therapy request to theimplanted device.

In response to the receipt of a patient therapy request, the implanteddevice begins timing a shock therapy delay time period. The shocktherapy delay time period may be pre-programmed by a physician, using anexternal programmer device, or programmed by the patient using a moresophisticated patient activator device. The delay time period ispreferably selected to be sufficiently long so as to allow a patientsufficient time to prepare for and/or mitigate the discomfort of atrialshock therapy to be delivered to the patient in response to the atrialshock therapy request. The shock therapy delay time period may thus beset from several minutes (to allow a patient time to take an analgesicor sedative, to lie down, or to begin exercising) to several hours (toallow a patient to go to sleep after requesting therapy so that shocktherapy is provided at night during sleep). After the shock therapydelay time period has expired, an appropriate atrial shock therapy isprovided by the implanted device. Preferably, such atrial shock therapyis provided only after confirmation by the implanted device of anongoing atrial arrhythmia event.

The patient activator communication device may also be employed tocontrol an implanted cardiac device withhold completely the providing ofatrial shock therapy by the device. For example, a patient therapyrequest may only be detected by the implanted device if a patienttherapy request signal is maintained for longer than a therapy requestsignal threshold duration, e.g., by maintaining a patient activatordevice magnet in position to operate the reed switch in the implanteddevice for more than the threshold duration. In such a case, the delaytime period may be timed in response to removal of the patient therapyrequest signal (e.g., removal of the patient activator from the implantsite) and an appropriate shock therapy (e.g., synchronized cardioversionand/or antitachycardia pacing, depending upon the nature of the atrialarrhythmia) provided by the implanted device after expiration of thedelay time period and confirmation of an ongoing atrial arrhythmia. Ifthe patient activator device is removed from near the implantation siteshortly after it is applied (i.e., within less than the therapy requestsignal threshold duration from initial application of the activator tothe implantation site), atrial shock therapy will be withheld (i.e.,disabled), and no atrial shock therapy will be provided even though anatrial arrhythmia, has been detected and atrial shock therapy isotherwise available. If the providing of atrial shock therapy iswithheld in this manner, the patient may use the activator communicationdevice to initiate delayed patient requested atrial shock therapy at alater time which is more convenient or appropriate for the patient.

Although a relatively simple and inexpensive patient activator device,e.g., including a magnet, may be employed in accordance with the presentinvention, a more complicated patient activator may also be used. A morecomplicated patient activator communication device may include areceiver/transmitter for communicating control signals to the implantedcardiac device via a telemetry (e.g., RF) link with a correspondingreceiver/transmitter in the implanted device. Such a patient activatorcommunication device may include a patient input circuit, includingbuttons, switches, etc., for allowing a patient to signal via thetelemetry link from the activator to the implanted device a patienttherapy request. A patient may employ such a patient activatorcommunication device to provide different types of therapy requests tothe implanted device to request either immediate atrial shock therapy,or delayed shock therapy, as described above. For example, using such anactivator device, a patient therapy delay request may be provided by thepatient to the implanted device. In response to receipt of the patienttherapy delay request, shock therapy is provided by the implanted deviceafter timing a shock therapy delay period (after the delay periodexpires and an ongoing atrial arrhythmia is confirmed). In contrast,atrial shock therapy may be provided to the patient by the implanteddevice immediately following receipt of a patient therapy request fromthe activator in which no therapy delay is requested. Such a patientactivator may also be employed by the patient to provide a shock therapydelay period setting command to the implanted device, thereby to set theshock therapy delay period to a time period desired by the patient.

Further objects, features, and advantages of the invention will beapparent from the following detailed description taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an exemplary implantable cardiac devicefor detecting atrial arrhythmias and providing electrical shock therapyto the atria, and a patient activator communication device forcontrolling the implantable device to provide atrial shock therapy afterexpiration of a delay time period in accordance with the presentinvention.

FIG. 2 is a more detailed schematic diagram of an exemplary patientactivator communication device which may be used to request delayedatrial shock therapy in accordance with the present invention.

FIG. 3 is flowchart diagram illustrating an exemplary method forrequesting delayed atrial shock therapy from an implanted cardiac devicein accordance with the present invention using a patient activatorcommunication device.

DETAILED DESCRIPTION OF THE INVENTION

An exemplary implantable cardiac device 10 which may be controlled by apatient activator communication device 12 to provide delayed patientcontrolled atrial shock therapy in accordance with the present inventionis illustrated in, and will be described in detail with reference to,FIG. 1. Although described in detail herein with reference to animplantable device 10 having the primary function of detecting andtreating atrial arrhythmias, it should be understood that the presentinvention may be employed with an implantable device which also performsother functions, such as ventricular monitoring and therapy and singleor dual chamber bradycardia pacing.

The implantable cardiac device 10 includes a hermetically sealedcanister 14 which encloses circuitry for detecting and analyzing cardiacarrhythmias and for providing electrical shock therapy to treat sucharrhythmias. The circuitry within the canister 14 is connected via oneor more leads 16 to one or more electrodes 18 which are implanted in ornear the chambers of a patient's heart 20. The electrodes 18 pick upelectrical signals produced in the chambers of the heart 20 and provideelectrical contact for electrical pulses or shocks which are deliveredto the chambers of the heart 20 to pace or defibrillate/cardiovert theheart 20. Depending upon the specific applications and functionality ofthe implantable cardiac device 10, electrodes 18 may be positioned in ornear the atria, ventricles, or, preferably, both the atria andventricles of the heart 20. In an implantable cardiac device 10 inaccordance with the present invention for detecting atrial arrhythmias,and providing atrial shock therapy to terminate such atrial arrhythmias,for example, electrodes 18 are positioned in or near the atrial, fordetecting atria activity and providing atrial shock therapy to theatria, as well as in the ventricles, for detecting ventricular activity,e.g., for use in verifying the presence of atrial arrhythmias and insynchronizing the providing of atrial cardioversion shock pulses to theatria with ventricular events. A plurality of leads 16 may be requiredto connect the electrodes 18 positioned in the heart 20 to the circuitrywithin the device canister 14. As is known in the art, multipleelectrodes 18 may be coupled to the circuitry within the canister 14 viaa single one of the leads 16. The canister 14, leads 16, and electrodes18 are preferably designed such that the entire device 10 is implantablebeneath the skin of a patient.

The leads 16 connect the electrodes 18 positioned within the heart 20 tosignal detection circuitry 22 within the implantable device canister 14.The signal detection circuitry 22 may be implemented in a conventionalmanner to provide atrial and/or ventricular activity signals based onthe cardiac signals picked up at the electrodes 18. Conventional signaldetection circuitry 22 may include signal amplifiers and filters, andmay include, in addition, circuitry for detecting atrial and ventriculardepolarizations and for providing atrial and ventricular depolarizationdetection indication signals in response thereto, along with circuitryfor obtaining electrogram signals and for providing digitizedelectrograms from the cardiac signals detected at the electrodes 18.

The signals provided by the signal detection circuitry 22 are providedto an implantable device system processor 24. The system processor 24may be implemented, for example, as one or more conventionalmicroprocessors with associated memory 26. Memory 26 may be an integralpart of, or separated from, but coupled to, the processor 24. Memory 26is employed in a conventional manner to store data, such as cardiacactivity data, for analysis by the processor 24, well as to store theprogramming instructions which control the functions performed by theprocessor 24. For example, programming instructions for implementing anatrial arrhythmia detection algorithm 28 by the processor 24, foroperating the processor 24 to generate messages 30 for indicating thereceipt of a patient therapy request from the patient activatorcommunication device 12, and for timing time periods such as a therapydelay period 31, etc., may be stored in memory 24. These functions willbe described in more detail below. Of course, other general andconventional programming instructions for the processor 24 may also bestored in memory 26.

The implantable cardiac device 10 also includes conventionalcardioverter/defibrillator circuitry 32 for applying electrical energyto the heart 20 via the leads 16 and electrodes 18 positioned in theheart. In response to the detection of an atrial arrhythmia by theprocessor 24, based on cardiac signals provided by the signal detector22, the processor 24 controls the cardioverter/defibrillator 32 toprovide electrical shock therapy to the heart 20 to terminate the atrialarrhythmia event. The type of electrical shock therapy provided to theheart 20 may depend upon the type of atrial arrhythmia event identified.For example, the cardioverter/defibrillator circuitry 32 may becontrolled by the processor 24 to provide a relatively high voltagelevel atrial defibrillation pulse to the atria of the heart 20 toterminate an atrial fibrillation or flutter event. Such relatively highvoltage shock therapy is preferably provided in synchronism with adetected or paced ventricular event, in order to prevent the atrialshock therapy from initiating a more serious ventricular arrhythmia. Inresponse to the detection of a high-rate, but more regular, atrialarrhythmia, e.g., atrial tachycardia, the processor 24 may control thecardioverter/defibrillator circuitry 32 to provide atrialantitachycardia pacing to the atria to terminate the atrial arrhythmiaevent. Atrial antitachycardia pacing may typically include a rapidseries of atrial pacing pulses delivered to the atria via a pacing lead16 and one or more electrodes 18 positioned in or near the atria of theheart 20. Various atrial shock therapies are known to those skilled inthe art, and will not be described in further detail herein. Asdiscussed above, atrial shock therapy, especially atrial defibrillationshock therapy, can be very uncomfortable for the patient receiving it.Such discomfort can be mitigated by the patient, however, such as bytaking an analgesic or sedative before therapy is provided, or byexercising during the delivery of atrial shock therapy.

The implantable device 10 may include receiver/transmitter circuitry 34including an antenna coil 36. The receiver/transmitter 34 may beimplemented in a conventional manner to transmit data from the systemprocessor 24 out of the implanted device 10 to a remote programmerdevice 38. For example, cardiac activity data detected by the signaldetector circuitry 22 may be transmitted to the external programmerdevice 38 to be stored and analyzed therein in more detail than ispossible in the implanted device 10 itself. The receiver/transmitter 34may also receive programming instructions from the external programmerdevice 38 for, for example, programming operating parameters of theimplantable cardiac device 10. Communication between thereceiver/transmitter 34 and the external programmer device 38 may beimplemented in a conventional manner, e.g., via a telemetry (e.g., RF)link. It is noted that the external programmer device 38 is a relativelylarge and sophisticated device which is typically employed by aphysician to monitor and control operation of the implantable device 10.

In accordance with the present invention, the implantable cardiac device10 may also include a reed switch 40 mounted therein and coupled to thesystem processor 24. As will be discussed in more detail below, the reedswitch 40 is operated (closed or opened) by the application of amagnetic field near the site of implantation in a patient of theimplantable cardiac device 10. The system processor 24 detects theoperation of the reed switch 40 as a patient therapy request. Inresponse to the patient therapy request, the system processor 24initiates timing of a therapy delay period. After expiration of thetherapy delay period, the system processor 24 controls thecardioverter/defibrillator 32 to deliver atrial shock therapy to theheart 20 of the patient, preferably after confirming the presence of anongoing atrial arrhythmia.

In accordance with the present invention, the implantable cardiac device10 may preferably also include tone generation circuitry 42. The tonegeneration circuitry 42 may be implemented in a conventional manner, andis controlled by the system processor 24 to drive a small speaker 44 toproduce tones of sufficient volume to be audible by a patient in whichthe implantable device 10 is implanted. As will be discussed in moredetail below, the tones produced by the tone general circuitry 42 andspeaker 44 may be used to indicate to a patient that a patient therapyrequest has been received by the implanted device 10 from the patientactivator communication device 12.

The implantable cardiac device 10 also includes a battery 46, whichprovides power for the processor 24 and other circuit components of theimplantable cardiac device 10.

The circuitry for implementing the signal detector 22, processor 24,cardioverter/defibrillator 32, receiver/transmitter 34, tone producer42, and other functions of the implantable cardiac device 10 may beimplemented in a conventional manner using analog or digital circuitry,including one or more microprocessors, or any combination thereof. Aswill be known to those skilled in the art, functions performed by thesignal detector 22, cardioverter/defibrillator 32, receiver/transmitter34, and tone producer 42, may be performed by independent analog and/ordigital circuitry, as suggested by the illustration of FIG. 1, or may beimplemented in one or more processors 24, or with a combination ofindependent circuits and one or more processors.

In accordance with the present invention, a patient in which theimplantable cardiac device 10 is implanted may employ a patientactivator communication device 12 to request the delayed providing ofatrial shock therapy by the implanted device 10. The patient activator12 preferably designed to be portable, and is preferably small in sizeand able to be held easily in the hand and manipulated by a patient.Various components which may be implemented in an activator 12 inaccordance with the present invention are illustrated schematically inFIG. 2.

The activator 12 may preferably include a magnet 48 mounted therein. (Inits simplest form, a patient activator 12 in accordance with the presentinvention may be implemented with a magnet 48 alone). When the patientactivator 12 is positioned near the implant site of the implantabledevice 10, the magnetic field generated by the magnet 48 in theactivator 12 operates the reed switch 40 coupled to the processor 24 inthe implantable device 10. Operation of the reed switch 40 in thismanner for at least a minimal period of time, e.g., two seconds, isdetected by the implanted device processor 24 as a patient therapyrequest which initiates the timing of a shock therapy delay period bythe processor 24, followed by the providing of atrial shock therapy. Theprocessor 24 may preferably employ the message generator function 30 togenerate a message which is provided to the patient to indicate that thepatient therapy request has been received by the implanted device. Sucha message may be provided to the patient, as described above, bycontrolling tone generation circuitry 42 in the implantable device 10 togenerate a tone audible to the patient to indicate that the patienttherapy request has been received and that the requested and appropriateaction will be taken by the implantable device 10 in response thereto.

The message generated by the implantable device 10 to indicate that apatient therapy request, or other command, has been received thereby mayalso preferably be provided in a visual form to the patient, e.g., in avisual display provided on the patient activator 12. For example, theactivator 12 may include tone detection circuitry 50. The tone detectioncircuitry 50 may be implemented in a conventional manner to detect thetones produced by the tone generation circuitry 42 in the implantablecardiac device 10, and to generate electrical signals in responsethereto. The electrical signals generated by the tone detectioncircuitry 50 in the activator 12 may be provided to an activatorprocessor 52, which decodes the signals provided by the tone detectioncircuitry 50. The activator 12 also includes conventional displaycircuitry 54. The display circuitry 54 may be driven by the activatorprocessor 52, in response to the signals received from the tonedetection circuitry 50, to provide a visual indication to the patientconfirming receipt of a patient therapy request by the implantablecardiac device 10. For example, the display circuitry 54 may include oneor more LEDs or lamps 56 which are illuminated in a conventional mannerto indicate, e.g., that a patient therapy request has been received bythe implanted device 10 from the activator 12.

As an alternative to the magnet 48, for providing a patient therapyrequest to the implanted cardiac device 10, and tone detector circuitry50, for detecting an audible message indicating that a therapy requesthas been received by the implanted device 10, the activator 12 mayinclude conventional receiver/transmitter circuitry 58, including anantenna 59. The activator receiver/transmitter 58 may be implemented ina conventional manner, and may be coupled to the receiver/transmitter 34(or another similar circuit) in the implanted device 10, via a telemetry(e.g., RF) link, to both provide patient therapy request signals to andreceive confirmation of the receipt of such requests from the implantedcardiac device 10. The activator receiver/transmitter 58 may be coupledto, and controlled by, the activator processor 52. Patient inputcircuitry 60 is preferably also provided in the activator 12 and coupledto the activator processor 52. The activator input circuitry 60 mayinclude conventional buttons, switches, dials, etc., and relatedelectronic circuitry. A patient employs the activator input circuitry 60to initiate patient therapy request. For example, the patient may push abutton on the activator 12, which is part of the input circuitry 60, torequest the delayed providing of atrial shock therapy by the implanteddevice 10. A signal generated by the activator input circuitry 60 isreceived by the processor 52 which, in turn, generates a command signalrequesting, e.g., the delayed providing of atrial shock therapy by theimplanted device 10. This command signal is, in turn, provided to theactivator receiver/transmitter 58, to be transmitted to the implanteddevice 10, e.g., via the receiver/transmitter 34 therein, over thetelemetry link. The received command signal is, in turn, processed bythe implanted device processor 24. In response to the request, a messageindicating, e.g., that the patient therapy request has been received, isgenerated by the implanted device processor 24, and provided to theimplanted device receiver/transmitter 34 for transmission back to theactivator 12. This confirmation message is received by the activatorreceiver/transmitter 58 and provided to the activator processor 52. Theactivator processor 52 processes the confirmation message received fromthe implanted device 10, and generates therefrom an indication that apatient therapy request has been received by the implanted device 10,which, e.g., may be presented to the patient by controlling theactivator display 54. Of course, the confirmation indication may beprovided visually, audibly, and/or in any other manner to a patient onthe activator 12. The activator input 60 and receiver/transmittercircuitry 58 may also be employed to request immediate, rather thandelayed, atrial shock therapy from the implanted device 10, to instructthe implanted device to withhold the providing of atrial shock therapy,and/or to allow the patient to set the shock therapy delay period, aswill be described in more detail below. It should be noted that apatient activator 12 will typically include either thereceiver/transmitter 58 and input circuitry 60 or a magnet 48 and tonedetector 50, but may include both systems, as illustrated in FIG. 2.

An exemplary process in accordance with the present invention forcontrolling an implanted cardiac device 10 to provide delayed atrialshock therapy following a patient controlled atrial shock therapyrequest will now be described in detail with reference to the exemplaryflowchart diagram of FIG. 3. In accordance with the present invention,as discussed above, a patient employs a patient activator 12,implemented using either a magnet 48 for operating a reed switch 40 inthe implanted device 10, or an input circuit 60 and receiver/transmitter58 forming a telemetry link with the implanted device 10, to provide apatient therapy request to the implanted device 10. A patient therapyrequest provided by the patient using the activator 12 and detected bythe implanted device 10 controls the implanted device 10 to providedelayed atrial shock therapy, giving the patient sufficient time toprepare for receipt of the therapy, to mitigate therapy discomfort. Aswill be discussed in more detail below, the patient therapy request mayalso be used to control the implanted device 10 to withhold entirely theproviding of atrial shock therapy, which may be enabled at a later timeby the patient, and/or to request the immediate delivery of atrial shocktherapy by the implanted device 10, without a delay. Each of theseoptions is considered in the exemplary flowchart diagram of FIG. 3. Itshould be understood, however, that an implantable patient controllableatrial shock therapy device in accordance with the present inventionneed not provide each and every one of these patient control options.The ability of a patient to control the implantable device 10 in anymanner to be described herein may be enabled or disabled, e.g., by aphysician. This may be achieved by programming the implanted device 10,e.g., using the external programmer device 38.

The exemplary process illustrated in FIG. 3 employs two timers. Atherapy request timer is employed to time the duration of the presenceof an activator magnet 48 near the implant site of the implanted device10. Thus, the therapy request timer is employed to time the duration ofoperation of the reed switch 40 in the implanted device 10 by the magnet48. As will be described in more detail below, use of the therapyrequest timer allows a patient to use a simple activator device 12including magnet 48 to request either the delivery of delayed atrialshock therapy by the implanted device 10 or to withhold the providing ofatrial shock therapy by the implanted device 10. The therapy delay time31 is employed to time the therapy delay period in response to detectionof patient therapy request. Atrial shock therapy may be delivered by theimplanted device 10 to the patient after expiration of the therapy delayperiod. Both the therapy request and therapy delay timers may beimplemented in or controlled by the implanted device processor 24 andmay, of course, be either up or down timers. The therapy request andtherapy delay timers are initially reset at step 68.

The implanted device processor 24 continually detects for the receipt ofa patient therapy request originating from external to the implantabledevice 10 at 70. As discussed above, the patient therapy request may beprovided by positioning an activator magnet 48 near the implant site ofthe implantable device 10, to operate the reed switch 40 in theimplantable device 10. If a patient therapy request is detected in thismanner, the therapy request timer is incremented at 72 as long as thepatient therapy request, e.g., operation of the reed switch 40, isdetected. When the patient therapy request is no longer detected, e.g.,when the activator magnet 48 is removed from near the implant site ofthe implantable device 10, the implanted device processor 24 compares at74 the current value of the therapy request timer to a therapy requestsignal threshold duration. This threshold duration may be programmable,and may be, for example, approximately seven seconds. If the value ofthe therapy request timer indicates that the activator magnet 48 wasonly in position to operate the reed switch 40 for less than the therapyrequest signal threshold duration, the implanted device 10 may beinstructed to withhold the providing of atrial shock therapy at 76. Ifthe implanted device 10 is thus instructed to withhold the providing ofatrial shock therapy, the therapy request timer is reset at 68 and theimplanted device processor 24 continues to detect for the next patienttherapy request at 70. Thus, by employing the patient activator magnet48 to provide the patient therapy request signal for less than a therapyrequest signal threshold duration, a patient may control the implanteddevice 10 to withhold the providing of atrial shock therapy until thepatient again uses the activator 12 to request specifically theproviding of delayed (or immediate) atrial shock therapy by theimplanted device 10.

If the patient therapy request is provided for longer than the therapyrequest signal threshold duration, i.e., if the therapy request timer isdetermined at 74 to have a value greater than the threshold value, theproviding of delayed atrial shock therapy by the implanted device 10 isrequested. If the providing of delayed atrial shock therapy isrequested, the therapy delay timer 31 is incremented at 78 and checkedat 80 to determine if the value of the therapy delay timer equals theselected therapy delay period. The function of these steps 78 and 80 is,therefore, to time a shock therapy delay period following and inresponse to receipt of a patient therapy request by the implanted device10. The therapy delay period may be preprogrammed by a physician, usingthe programmer device 38, or selectable by a patient, as will bediscussed in more detail below. The therapy delay period is preferablyselected to be sufficiently long so as to allow a patient to prepare forthe requested atrial shock therapy after such a request is made. Thisallows a patient to take action to mitigate therapy discomfort by, e.g.,taking analgesics or sedatives, lying down, or taking other measures,such as exercising to mitigate shock perception. The shock therapy delayperiod may be set to a duration of minutes to several hours. A shocktherapy delay period of several hours would allow a patient, forexample, to employ the activator 12 to request delayed atrial shocktherapy before going to sleep in the evening, thereby delaying shocktherapy for a sufficient duration such that the implantable device 10provides atrial therapy shocks at night during the patient's sleep.

After expiration of the shock therapy delay period, the implantabledevice 10 initiates atrial shock therapy at 82. The step of initiatingatrial shock therapy 82 may preferably include confirmation of theongoing presence of an atrial arrhythmia by the implanted deviceprocessor 24 using, e.g., conventional atrial arrhythmia detectionalgorithms 28. If an atrial arrhythmia is confirmed, the processor 24may control the cardioverter/defibrillator 32 to provide an appropriateatrial shock therapy to the patient's heart 20 to terminate the atrialarrhythmia detected. As discussed above, atrial shock therapy mayinvolve the application of a relatively high voltage level atrialdefibrillation pulse to the patient's heart 20, preferably insynchronism with a detected or paced ventricular activation, toterminate atrial fibrillation or flutter, or a train of atrialantitachycardia pacing pulses, to terminate a high rate but more regularatrial tachycardia.

Where the patient employs a patient activator 12 which includes input 60and receiver/transmitter circuitry 58 for providing command signals tothe implanted device 10 over a telemetry link, specific instructions maybe selected by the patient, using the input circuit 60, and provided tothe implanted device 10 over the telemetry link, to either request orwithhold the providing of atrial shock therapy. Thus, if such anactivator device 12 is employed, there may be no need to employ thetherapy request timer, as described above. Using such an activatordevice 12, a patient may also be enabled to provide a patient therapyrequest signal to the implanted device 10 in response to which atrialshock therapy is provided to the patient immediately (following theconfirmation of an ongoing atrial arrhythmia) rather than following thetiming of a shock therapy delay period. For example, at step 84 (FIG. 3)the implantable device processor 24 may determine whether the patienttherapy request telemetered from the activator 12 is a request for theproviding of immediate atrial shock therapy or delayed atrial shocktherapy. If a patient therapy delay request is indicated, the implanteddevice processor 24 begins timing the shock therapy delay period 78, 80,after the expiration of which shock therapy is initiated 82. Incontrast, if the patient therapy request telemetered from the activator12 does not indicate a request for the providing of delayed atrial shocktherapy, the implanted device processor 24 initiates the providing ofatrial shock therapy at 82 immediately, without first timing the shocktherapy delay period.

A patient activator 12 in accordance with the present invention whichincludes input 60 and receiver/transmitter circuitry 58 may also beemployed by a patient to set the shock therapy delay period, the periodbetween the receipt of a patient therapy request from the patient by theimplanted device 10 and the delivery of atrial shock therapy to thepatient by the implanted device 10, to a desired shock therapy delayperiod duration. For example, the patient may employ the input circuitry60 to select a desired shock therapy delay period duration. In response,a shock therapy delay period setting command, indicating the desiredshock therapy delay period, is generated by the activator processor 52and transmitted from the activator 12 via the receiver/transmitter 58 tothe implanted device 10. In response to receipt of the telemetered shocktherapy delay period setting command, the implanted device processor 24sets the shock therapy delay period to the desired delay period selectedby the patient. Thus, a patient may be allowed both to control andspecify the amount of delay to therapy following a patient therapyrequest.

It should be understood that the present invention is not limited to theparticular exemplary embodiments and applications thereof illustratedand described herein, but embraces such modified forms thereof as comewithin the scope of the following claims. In particular, it should beunderstood that not all of the steps illustrated schematically in FIG. 3need be performed, and the steps illustrated may be performed in adifferent order, in accordance with the present invention.

1. An implantable device for providing atrial shock therapy controllableby a patient using an external activator, the implantable devicecomprising: an atrial arrhythmia detector to detect an atrialarrhythmia; an atrial cardioverter/defibrillator to provide an atrialshock; a receiver/transmitter to receive a patient therapy request and adelay period from the external activator via a telemetry link; and aprocessor adapted to time the delay period between receipt of thepatient therapy request by the receiver/transmitter and providing theatrial shock and control the atrial cardioverter/defibrillator toprovide the atrial shock upon expiration of the delay period in responseto the patient therapy request being a request for a delayed atrialshock therapy, and to control the atrial cardioverter/defibrillator toprovide the atrial shock, without timing the delay period, in responseto the patient therapy request being a request for an immediate atrialshock therapy.
 2. The implantable device of claim 1, wherein theprocessor is adapted to generate a confirmation message indicating thatthe patient therapy request has been received.
 3. The implantable deviceof claim 2, wherein the receiver/transmitter is adapted to transmit theconfirmation message to the external activator.
 4. The implantabledevice of claim 2, further comprising tone generation circuitry and aspeaker to produce a tone indicating that the patient therapy requesthas been received, the tone audible by the patient.
 5. The implantabledevice of claim 1, wherein the processor is adapted to confirm apresence of the atrial arrhythmia before the providing of the atrialshock.
 6. The implantable device of claim 1, wherein the telemetry linkcomprises an RF telemetry link.
 7. A system for patient controllableatrial shock therapy, the system comprising: an implantable deviceincluding: a signal detector to provide cardiac activity signals; anatrial cardioverter/defibrillator to deliver an atrial shock; animplantable device processor, coupled to the signal detector and theatrial cardioverter/defibrillator, to control the delivery of the atrialshock in response to a patient therapy request, the implantable deviceprocessor adapted to time a delay period upon receipt of the patienttherapy request and initiate a delivery of the atrial shock uponexpiration of the delay period in response to the patient therapyrequest being a request for a delayed atrial shock therapy, and toinitiate the delivery of the atrial shock, without timing the delayperiod, in response to the patient therapy request being a request foran immediate atrial shock therapy; and an implantable devicereceiver/transmitter to receive the patient therapy request and thedelay period via a telemetry link; and an external patient activatorincluding: patient input circuitry to receive the patient therapyrequest and the delay period; and an activator receiver/transmitter totransmit the patient therapy request and the delay period to theimplantable device receiver/transmitter via the telemetry link.
 8. Thesystem of claim 7, wherein the implantable device further comprises amessage generator coupled to the implantable device processor, themessage generator adapted to generate a confirmation message confirmingreceipt of the patient therapy request.
 9. The system of claim 8,wherein the external patient activator further comprises a display,coupled to the activator processor, to present a visual indicationconfirming the receipt of the patient therapy request by the implantabledevice.
 10. The system of claim 9, wherein the patient input circuitryis adapted to receive a request for withholding the delivery of theelectrical energy.
 11. A method for operating an implantable cardiacdevice, the method comprising: detecting an atrial arrhythmia using theimplantable cardiac device; receiving an external patient therapyrequest and a delay period transmitted from an external activator to theimplantable cardiac device via a telemetry link; timing the delay periodand providing an atrial shock upon expiration of the delay period inresponse to the patient therapy request being a request for a delayedatrial shock therapy; and providing the atrial shock, without timing thedelay period, in response to the patient therapy request being a requestfor an immediate atrial shock therapy.
 12. The method of claim 11,further comprising confirming a presence of the atrial arrhythmia beforethe providing of the atrial shock therapy.
 13. The method of claim 11,further comprising generating a confirmation message indicating thereceipt of the patient therapy request by the implantable cardiacdevice.
 14. The method of claim 13, further comprising presenting anaudible tone using a speaker of the implantable cardiac device, theaudible tone indicating the receipt of the patient therapy request bythe implantable cardiac device.
 15. The method of claim 13, furthercomprising: transmitting the confirmation message from the implantablecardiac device to the external activator; and presenting theconfirmation message visually using the external activator.
 16. Themethod of claim 11, wherein receiving the external patient therapyrequest signal transmitted from the external activator to theimplantable cardiac device via the telemetry link comprises receivingthe external patient therapy request signal transmitted from theexternal activator to the implantable cardiac device via an RF telemetrylink.
 17. The method of claim 16, further comprising receiving anexternal patient request for withholding the providing of the atrialshock during the delay period.